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CLAUDE.md

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Build Commands

# Build with tests
./gradlew build

# Build without tests
./gradlew assemble

# Run all tests for a module
./gradlew :agent:test

# Run a single test
./gradlew :agent:test --tests "com.teamscale.jacoco.agent.MyTest.testMethod"

# Publish to local Maven repo (for local plugin testing)
./gradlew publishToMavenLocal

# Build Docker image
docker build -f agent/src/docker/Dockerfile .

# Compile for different JaCoCo version (don't commit unless upgrading)
./gradlew dist

Project Architecture

This is a multi-module Gradle project (Java 21 toolchain, targets Java 8) that provides a JVM profiler for collecting code coverage and uploading it to Teamscale.

Core Modules

  • agent - Main Java agent that instruments bytecode via JaCoCo and collects coverage
  • report-generator - Converts JaCoCo binary execution data to XML/testwise coverage formats
  • teamscale-client - HTTP client library for Teamscale server communication
  • tia-client - Test Impact Analysis client for identifying impacted tests

Build Tool Plugins

  • teamscale-gradle-plugin - Gradle plugin for coverage collection and test-wise execution
  • teamscale-maven-plugin - Maven plugin with equivalent functionality
  • impacted-test-engine - JUnit 5 engine that queries Teamscale for impacted tests

Agent Internals

Entry point: PreMain.premain() in agent/src/main/java/com/teamscale/jacoco/agent/PreMain.java

Initialization flow:

  1. JVM loads agent via -javaagent parameter
  2. PreMain.premain() parses options and initializes logging
  3. JaCoCoPreMain registers LenientCoverageTransformer with the JVM
  4. Classes are instrumented at load time with coverage probes

Coverage modes:

  • Interval-based (Agent class) - Periodically dumps coverage (default every 10 min)
  • Test-wise (TestwiseCoverageAgent class) - Per-test coverage via HTTP endpoints (/test/start, /test/end)

Key classes:

  • AgentOptions - Central configuration holder
  • JacocoRuntimeController - Interface to JaCoCo's execution data
  • LenientCoverageTransformer - Bytecode instrumentation with error recovery
  • IUploader - Interface for upload backends (Teamscale, Azure, Artifactory, disk)

System Tests

The system-tests/ directory contains integration tests that exercise the packaged agent JAR in various scenarios. Each subdirectory is a separate Gradle subproject.

Pre-Commit Checklist

Before completing any code change, verify:

  • CHANGELOG.md updated for user-visible changes (bug fixes, new features, breaking changes)
  • Tests added/updated for the change
  • No unintended files modified